This chapter reviews theoretical research on e-communication behavior, identifying two main types of theories: technological and social. Based on this review, it provides the rationale for the development of a new theory that is neither technological nor social. The new theory is based on evolution theory, whose foundations were laid out by Darwin. Three theoretical principles are developed from evolution theory: media naturalness, innate schema similarity, and learned schema variety. The chapter concludes by illustrating how the theoretical principles can be used as a basis for the development of a simple predictive model in the context of an online broker.